1. Field of the Invention
The present invention relates to a cable modem for use in, for example, cable TV (CATV) system and the like, and more particularly to a communication line connecting apparatus restricts the band used in communication line to be connected to a cable modem and a method of controlling the communication line connecting apparatus.
2. Description of the Related Art
Recently, the CATV system provides not only TV broadcasting service using the CATV network but also data communication service using a personal computer and a portable information terminal having a wireless communication function.
For example, if user intends to acquire his desired information from an information provider on Internet, he calls to a desired information provider from a personal computer. Then, the personal computer and CATV cable modem are connected through a wireless local area network (LAN) and then, the computer accesses a server of the information provider from the cable modem through CATV network, CATV broadcasting station and Internet. If a communication path is established between the personal computer and the server, information depending on a demand of the personal computer is transmitted from the server to the personal computer through the communication path.
In the above-described CATV system, a frequency band for use in communication on the CATV network is allocated from the CATV broadcasting station in the unit of cable modem depending on communication traffic on the CATV network (for example, Jpn. Pat. Appln. KOKAI Publication No. 2002-152709). Thus, the usage frequency band of the CATV network can be used effectively.
Plural personal computers are connected to each cable modem through wireless LAN. If only a personal computer is connected and low-speed mode communication is carried out, a specific frequency band is allocated to a single personal computer, so that a large band is consumed unnecessarily, thereby disabling a connecting demand from other personal computers from being met easily.
For the reason, a system capable of changing the width of the usage frequency band arbitrarily depending on high-speed/low-speed communication mode has been proposed (for example, Jpn. Pat. Appln. KOKAI Publication No. 8-228173).
However, the above-described system has such a problem that because the width of the frequency band is changed by the personal computer, a processing load on the personal computer increases due to the configuration of the personal computer. Further, no band condition set up between the cable modem and CATV broadcasting station can be reflected on the wireless LAN.